Cytokines are multi-functional cell growth/differentiation inducing factors controlling immune and hematopoietic reactions. The series of factors composing cytokines, are mainly produced by activated T cells, macrophages, or stromal cells and connect the cells of the lymphoid system and the hematopoietic system in a network, regulating the proliferation, differentiation, and functions of these cells. So far, a number of factors have been isolated as cytokines and apart from the factors themselves, antibodies and receptor molecules of those factors, or antibodies against those receptors, have been developed as therapeutic drugs and are in actual use.
For example, G-CSF, which has a neutrophil-proliferating function, is already in use as a drug for many diseases and leukopenia resulting from the treatment of these diseases (K. Welte et al., the first 10 years Blood Sep. 15, 1996; 88:1907-1929 and also refer GENDAIKAGAKU ZOUKAN no. 18, Cytokine, edited by TOSHIAKI OHSAWA, 1990, published by TOKYO KAGAKU DOUJIN). Furthermore, an antibody against the receptor of IL-6, which acts in immune functions and inflammation, is being developed as a potential therapeutic drug against rheumatism and leukemia.